Letter to the press about new flood hazard

Here is the letter I sent . . .

I have sent you a copy of our email to Stephen Belli about this new flooding hazard for Seaton.  I am now sending you the supporting diagrams and explanatory argument.   Much of this is discussed on our blog at http://www.tescowatchseaton.blogspot.com/, but this had no pictures and these are essential to understanding our concerns.
 

Look at T1 above  This is taken from the sucessful Tesco planning application and shows the overall layout of the whole regeneration site.  Important here is the role of the flood relief channel, which I have marked.  

This runs from Harbour Road at the bottom of the picture (south) to the marshes at the top (north).  Harbour Road is the lowest part of Seaton and most susceptible to flooding from the sea or river.  This danger is greatly increased by raising the regeneration site and so stopping flood water draining north to the marsh.  To reduce this danger, the Tesco plan provides a flood relief channel (also called a monsoon drain or berm) running north-south right through the development site at low level, so cutting the site into two halves.

When the site is raised and a flood comes, water can flow from Harbour Road to the marshes along this channel.  Without the channel, raising the site means a serious increase in the flood risk for the whole area, which is largely residential.  We were not terribly happy about this solution, but it is better than nothing.

Now look at T2.  This shows Tesco's proposal to raise the whole site by pumping in infill from the sea.  The idea is to build a high wall right round the site, pump in a mix of seawater and aggregate along the black pipeline grid, allow it to settle, collect the seawater in a lagoon (blue arrows) and then pump it back out to sea.

The flood relief channel (FRC) is visible (and dotted by me), along with all the later buildings, so they seem to have just pasted their proposals on top of an earlier version of T1 without paying attention to the details.  They clearly have no understanding of the function of the FRC, as both the black pipeline and the blue water arrows flow straight over it, and it will be filled up with the rest of the site.  Without the FRC, the only flood protection device is lost and the whole area is at enormously greater risk of flooding.

We complained about this to the Environment Agency.  The correspondence is covered in the blog but, basically, they said leave it to the Tesco engineers.  But we can see no economic solution, and after 5 weeks, nor (it seems) can they.

Consider the options.

1.  Fill the site in two halves, on either side of the FRC.  This will require two separate filling operations, with separate piping and drainage lagoons.  It might be possible, but it is going to be very slow and very much more expensive.

2.  Fill the whole site and then dig out a new FRC.  This has two objections.

• While the site is being filled, there is no FRC.  If a flood comes along during the filling process, Harbour Road has no protection.
• Digging a channel through slippery sediment deposited from seawater is not going to be easy - and may be actually impossible.

There is no official acknowledgement of these problems, nor of the hazard to Seaton.  The Tesco contractors have made mistakes in the past (see the blog) and we are worried that they may be about to make another one - with potentially catastrophic results.

 We want EDDC and the EA openly to acknowledge the problem and tell us how they propose to deal with it.  Under these circumstances, we can only appeal to the power of the press and public opinion to bring this about.

No satisfaction yet on wall safety and flooding hazard

On 8th March (see below) we flagged up a new flood hazard presented by the Tesco scheme, and wrote to the Environment Agency on 9th March for their reaction.  In addition, we asked about the safety of the high temporary walls to be built around the site.  For several weeks there was silence - presumably while the EA consulted the Tesco consultants.  Then, on 25th March, we received their reply.

On the issue of the wall safety they say . . . "The use of hydraulic fill is a well established civil engineering technique and has been used to fill dams and move aggregates and minerals for many years. We are currently unaware of any examples where this technique has been used to fill prospective development sites in the manner being suggested in Seaton.  You may wish to search the internet for examples as they may exist.  However, we cannot rule this technique out as a possible solution to the raising the site in an efficient and timely manner.   Civil liability would rest firmly with the consultants/contractors in the event of any problems occurring.

The integrity of any temporary impounding banks is largely a matter for the consulting engineers, to satisfy themselves upon as part of any overall scheme design.  We must wait to consider any proposal that Jubbs wish to promote but shall at all times seek to protect the local environment and ensure as far as we are able that any proposal is safe.  "

To summarise the reply on wall safety. . .

1. This site infill method is unknown to them
2. If anything goes wrong, sue Tesco
3. It is up to the consultants (Jubbs) to decide on the quality of their own work
4. The EA will ensure safety as far as they are able, but no further.

Now, Jubbs are a well-known firm of engineering consultants who advised Liatris, the previous potential developers of this site.  However, anyone can make a mistake, and we were able to find a serious flaw in their flood risk analysis for Liatris.  By using an outdated version of our old friend PPS25, they proposed a much smaller (hence cheaper) infill volume than was actually required by law.  This was not noticed by the EA, nor by EDDC . . . it was left to our small team of amateurs to detect and correct it.  Our correction was then enforced without explanation or apology.

Now we are looking at a much more ambitious procedure - totally new and untried on this kind of site (says the EA). Who is to say that Jubb may not make another mistake - as they did before?  Who is going to be checking their work ?  Only the EA, as far as they are able; and how far is that ?  Judging from past performance, and the letter above - not very far at all.

Tescowatch will do it's best; but without access to the site or professional advice we may miss something.  It would be far better for the regulating authority (EA) to take on this role with committment and enthusiasm on behalf of us all - as is their function.

As far as flood protection during construction is concerned, the EA reply says . . . " Separate drainage proposals would need to be agreed prior to the main body of work proceeding. Consideration would have to be given to adverse weather, impact on watercourses and potential impact on groundwater.  We understand Jubbs have been considering a number of options to fill the site so we do not wish to speculate upon which, if any, might meet with our approval. "

This sounds reasonable enough (if rather vague), except for the fact that several site plans have already been tabled by Tesco - and approved by the EA - which show no flood protection at all during the infill phase.  Why was this problem not raised by the EA at that stage ?  Why did it have to wait for us amateurs to query it ?

No-one doubts the expertise available to the EA. Why won't they use it ?